This invention relates to a blood collection device for receiving a sample of blood from a patient but for preventing the blood from flowing out of the device once it has been received, and more particularly concerns a blood collection assembly with a unidirectional flow valve which is operable to open and close depending upon the pressure gradient on respective sides of the valve and thus control the collection of blood in the device.
Blood samples, for clinical or the like evaluation and testing, are commonly taken from the patient and collected in a suitable collection device such as a glass vial or tube. The blood collecting tube has been evacuated to produce a vacuum therein according to techniques which are conventional in the art. A rubber or similar stopper is provided in the tube so that it can be pierced by a needle on the other end of a similar needle inserted in the patient's vein for taking the sample. Under normal conditions the venous pressure will be greater than the pressure inside the evacuated tube thereby causing the blood to flow from the patient's vein, through the transfer needle system and into the blood collection tube.
Once the sample has been collected in the suitable tube, it is desirable to retain it there and prevent it from backflowing through the needle system and into the patient. Oftentimes the evacuated tube may contain an ingredient for mixture with the incoming blood for purposes of laboratory tests. Should this ingredient backflow into the patient's vein it may produce some unwanted problems. In addition, even though there may be no extra ingredient in the evacuated tube, for sanitary and other purposes it has been found desirable to prevent any backflow of blood from the collection tube. Various techniques are known and used to prevent this backflow of blood from the collection tube. One-way flow valves have been proposed which would operably open and allow the flow of blood to enter the evacuated collection container, but which would operably close to prevent the undesirable backflow of blood toward the patient. Typically, however, a one-way flow valve of this type has been incorporated in the needle assembly which collects the sample of blood from the patient and then deposits the same in the collection tube. The needle assembly of this type includes one or more needles, one end for insertion into the patient's vein, the other end (or other needle) for penetration through the rubber stopper on the collection tube. Somewhere between the two ends of the needle or needles is a one-way flow valve which is operable to allow blood flow through the needle toward the collection tube, but not back toward the patient. Examples of this general type of needle arrangement incorporating a one-way valve are found in U.S. Pat. Nos. 3,874,367; 3,659,587; 3,557,778. Other devices have been proposed wherein the stopper in the collection container is utilized for the one-way control of blood flow. In these devices, the valve is incorporated directly in the stopper or closure of the collection container, preferably in combination with the needle or passageway communicating with the interior of the container. These type valve devices are found in U.S. Pat. Nos. 3,162,195 and 2,551,315.
Placing a one-way valve in the needle or needle assembly as suggested by the above typical references often requires miniaturization and sophisticated designs inasmuch as the area for inclusion of the valve is generally small. This oftentimes increases expense and difficulty of manufacture. Thus, it can be seen that there is room for improvement in incorporating one-way flow valves in blood collection systems.